Persian Baked Omelette

Name: Persian Baked Omelette
Ingredients: 2 tablespoons olive oil; 1 tablespoon unsalted butter; 1 large red onion, halved and thinly sliced; 4 green onions, white and pale green parts only, finely chopped; 2 cloves garlic, finely chopped; 2 ounces baby spinach, coarsely chopped; 1/4 cup finely chopped fresh chives; 1/4 cup fresh cilantro leaves, finely chopped; 1/4 cup fresh flat-leaf parsley leaves, finely chopped; 2 tablespoons finely chopped fresh dill; Kosher salt and freshly ground black pepper; 1/4 cup pine nuts; 9 large eggs; 1/4 cup whole milk or half-and-half; 1 cup Greek yogurt, for serving, optional